Articulated ladder



May 10, 1955 L R, MCGQWEN 2,708,064

ARTICULATED LADDER Filed Aug. 13, 1952 INVEN TOR.

Lebng d R. ML Galvan BY ATTORNEY United States PatentO ARTICULATEDLADDER Leonard R. McGowen, East Alton, Ill., assignor to Standard OilCompany, Chicago, Ill., a corporation of Indiana Application August 13,1952, Serial No. 304,116

'3 Claims. (Cl. 228 -23) This invention relates to an articulatedladder. More particularly it relates to a ladder for traveling betweenthe top of a floating roof tank or the like and its roof, Which ladderautomatically adjusts for variation in roof height and embodies aplatform at the juncture of ladder sections which is constantlyhorizontal.

The roof of a floating roof tank varies its distance from the top of thetank depending upon tank content. Various automatically adjustableladders have been proposed for use in traveling between the roof and thetop of the tank but most of these require roller guideways on thesurface of the roof or other fixtures which complicate the structure aswell as interfere with the removal of snow. An additional disadvantageof most ladders of the prior art is that they are unsuitable for use intanks which are taller than they are Wide.

It is an object of the present invention to provide an automaticallyadjustable ladder for fluid storage tanks and the like having avertically movable roof which ladder is particularly adapted for use insuch tanks having a height which exceeds the diameter. A further objectof this invention is to provide an adjustable ladder embodying a safetyplatform at the juncture of each pair of its articulated sections, whichplatform remains substantially horizontal irrespective of roof position.These and additional objects will be apparent from the followingdetailed description.

The invention will be described in conjunction with the drawings inwhich Fig. 1 is a partially diagrammatic plan view of the floating rooftank showing the relation of the novel ladder thereto.

Fig. 2 is a partially diagrammatic vertical section through the tankshown in Fig. 1 taken along 2-2.

Fig. 3 is an enlarged perspective view of the novel ladder and platformapart from the tank and roof.

Fig. 4 is a detailed partial view of the articulated platform supports,the shaft and the roller.

Referring to Fig. 1, indicates a volatile liquid storage tank having afloating roof 11 adapted to float on the liquid in tank 10. A spiralstairway 12 permits ascent from the ground to the upper edge of the tankat which is positioned platform 13. Hingedly attached to platform 13 isladder section 14 which in turn is hingedly connected to platform 15.Juxtaposed to ladder section 14 is ladder section 16 which is similarlyhinged to platform 15 as well as being hinged to section 14. Section 16is hingedly connected to roof 11 at 17.

Referring now to Fig. 2 and Fig. 3, the components of the ladder andtheir relationship to the tank and roof can be more readily observed.Platform 15 is supported, at its unhinged end, upon support 18 which ispivotally connected to two sets of articulated support members 19 and 20at each end of shaft 21. The other ends of articulated support members19 and 20 are pinned to the stringers of the ladder sections 14 and 16and supports 22 thereof, respectively. For purposes of the presentdescription and the appended claims, the term ladder 2,708,064 PatentedMay 10, 1955 sections shall include supports 22. The action of thearticulated supporting structure for platform 15 is such that shaft 21and the axis of articulation of ladder sections 14 and 16 remains insubstantially the same horizontal plane, irrespective of roof position.To accomplish this, support members 19 and 20 are preferably of equallength and are pivotally connected to the stringers and supports 22 atan equal distance from the axis of articulation. Platform support 18comprises roller 23 and shaft 21. Roller 23 is rotatable about shaft 21on bearings disposedat each end thereof. Short rollers at each end ofthe shaft are equally suitable. It is preferred to employ a roller suchas that shown or other suitable friction reduction means upon which, theplatform may ride. Such is not essential, however, and the platform maybe slidably disposed on a simple nonrotatable cross member, e. g. shaft21. Inasmuch as the horizontal relationship of shaft 21 and the axis ofarticulation of the ladder sections remains constant, platform 15 whichis hinged to the ladder sections along said axis of articulation anddisposed upon roller 23 at itsopposite end, likewise remainssubstantially in the same plane as the ladder opens and closes.

One skilled in the art can readily conceive alternatives for maintainingthe platform horizontal without departing from the scope of the presentinvention. Thus, the platform support, instead of actually bearing theWeight of the platform, may be disposed in the space between the laddersections. There, the horizontally movable platform support (similarlyconnected to the articulated supporting structure) may travel back andforth on top of an extension of the platform which likewise protrudesinwardly from the axis. By providing that the weight of the platform isin substantial excess of such an extension on the opposite side of theaxis of articulation (which thus becomes a fulcrum), the extension isalways held in contact with the movable platform support and theplatform remains continually horizontal. Similarly, longitudinalguideways may be provided in one or more such extensions in which theend of the platform support may ride in a confined manner.

In Fig. 3 is shown the preferred construction of the ladder of thepresent invention. Sections 14 and 16 are strengthened by means ofsupport members 22 which are permanently afiixed to the ladder sectionsand in turn hinged to the platforms 13 and 15 and to roof 11.

In Fig. 4 is shown the manner in which articulated support members 1?and 20 are pivotally connected to shaft 21 and roller 23 is rotatablydisposed about shaft 21 on bearings 24 which are disposed within race25.

A person desiring to reach the roof from platform 13 may descend laddersection 14 to platform 15, cross over to section 16 and readily descendto the roof surface. While not essential, hand rails are preferablyincluded on the ladder.

The treads of the ladder may be narrow rungs as shown or of the widertread type which are weighted in such a way as to remain substantiallyhorizontal regardless of roof position. A ladder embodying such treadsis described in U. S. 1,944,159.

Whereas the embodiment of the ladder shown in the drawings and describedherein has only two sections, a greater number may, of course, beemployed. In such case a plurality of platforms equivalent to platform15 will be employed along the axis of articulation of each pair ofjuxtaposed ladder sections. It is preferred, although not essential,that all sections of a ladder be of substantially equal length. It islikewise preferred that articulated support members 19 and 20 be ofequal length and that they be pivotally connected to the ladder andtheir supports at an equal distance on either side of axis ofarticulation.

Having thus described my invention, what I claim as novel and desire toprotect by Letters Patent is as follows:

1. In a sectional ladder comprising articulated sections adapted topivotally engage the top of a tank and to span the top of the tank downto its vertically movable roof, said articulated sections expanding andcontracting vertically in accordance with the movement of the roof; theimprovement comprising a platform articulated to said ladder sections attheir axis of articulation, a horizontally movable support for saidplatform to maintain the same horizontal during the expanding andcontracting movement of said sections, and supporting elements pivotallyconnected to said movable support and the respective ladder sections tomaintain said support substantially horizontal with respect to said axisduring said expanding and contracting movements.

-2, The improved sectional ladder of claim 1 wherein frame memberscomprising stiles are disposed laterally and parallel to the stiles ofsaid ladder sections and are longitudinally coextensive therewith, saidframe members being articulated on the same axis of articulation as saidladder sections and said platform, and said frame member of one laddersection being substantially vertically aligned with a stile of theladder section articulated therewith.

3. The improved sectional ladder of claim 1 wherein the horizontallymovable platform support comprises a roller means.

Tuell Apr. 12, 1870 Jagschitz July 26, 1927

